We deeply thank Drs. Vavuranakis, Kalogeras, and Tousoulis for their interest in our recent paper (1). Any current intravessel optical coherence tomography (OCT) systems require injection of flushing medium, resulting in high pressure in the arterial lumen and consequently within the arterial wall. As we mentioned in the limitations section of our paper, intramural pressure gradient can result in compression of some of the vasa vasorum (VV) and intraplaque neovessels (2). Therefore, the images obtained of VV and intraplaque neovessels may not precisely reflect the same pressure condition. However, the high pull back speed (20 cm/s) of frequency-domain OCT brought about the short time period for maximal pressure flushing. Keeping in mind the variable volume of the VV and intraplaque neovessels, we analyzed all images for region of interest. It may not be necessary to determine ideal perfusion pressure because the correlations would likely be similar under the same conditions.

Contrast-enhanced ultrasound (CEUS) is also available for analyses of neovessels. Previously published data indicate that CEUS provides a significant increase in the signal-to-noise ratio and might permit enhanced identification of the vasculature within the vessel walls and within the plaque (3). However, for coronary arteries, the spatial resolution of CEUS seems to be enough for adventitial VV but unsatisfactory to depict intraplaque neovessels.

We agree that future studies are needed in the same segment and lesion to assess the serial role of the VV and neovessels. We think that the 3-dimensional structure transition of VV and intraplaque neovessels might have a clinical application to determine the progression of atherosclerotic plaque, whether using frequency-domain OCT or CEUS.

Footnotes

Please note: This work was supported by the Japan Society for the Promotion of Science KAKENHI Grant Number 24591068. Dr. Akasaka is an advisory board member of St. Jude Medical and Terumo; and receives research support from Abbott Vascular Japan, St. Jude Medical Japan, and Terumo. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.

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